It has long been known that rotary cutters can be utilized to sever substantially endless lengths of material into predetermined lengths for feeding into machines for further processing. These cutters generally involve the use of oppositely rotating rolls, one of which carries cutting blades and one of which serves as an anvil against which the material is cut by the blades. One particular environment in which this prior art has been utilized is in the processing of rubber in mills wherein a strip of material is fed along a conveyor after exiting an extruder or being fed from a storage source and then is fed between two opposed rotating rolls, one of which carries cutting blades or knives and which will sever the material against the opposed or anvil roll, permitting discharge of the severed piece to a further processing apparatus such as, for example, a mill.
With the advance in rubber technology, and particularly tire tread technology, the desire to insure longer life for the resulting tire has resulted in the use of a very high composition natural rubber which has a very high Mooney rating and which is very difficult to cut with the conventional arrangement. It is, of course, a definite problem when the knife on the rotating cutter engages the material against the anvil roll and fails to cut it. Obviously the result would be jamming or damage to the equipment in addition to the failure to sever the piece.
In the prior art, it is known that a greater or lesser gap between the cutting blades and the anvil roll can affect the cutting efficiency of the apparatus. Thus, one can ascertain the interference or gap required between the cutter and the anvil rolls to obtain maximum cutting efficiency depending on the thickness and composition of the particular material being cut. In the prior art, adjustments in this gap are commonly made by shaving or machining the cutter blade support body, thereby altering the relative centerlines of the rolls in order to establish that desired gap. It is also possible to grind the outer diameter of the rolls, but the drive gearing of the apparatus is such that the blades do not hit in the same place twice and the blades have a tendency to scrape rather than produce a clean cut. That is, the cutter roll is usually driven slightly faster than the anvil roll so that the leading edge bites into the material. This requires a very fine coordination and there is a risk of losing it if the outer diameters are altered.
In other words, the gap can be preset by controlling the dimensions of the cutter and/or the supporting structure in various ways. However, the difficulty with these approaches is that, at best, they only provide for one fixed gap dimension. Therefore, if a greater or lesser gap is subsequently desired, it is necessary to again shave off material from the cutter body or supporting structure to establish the larger gap and, of course, it is impossible to adjust to a smaller gap without replacing the entire cutter roll apparatus.
It has, therefore, become desirable to provide means for ready and quick adjustment of the gap between the cutter blades and the anvil roll so as to make it readily possible to accommodate different thicknesses and hardnesses of the material to be cut while maintaining a precise cutting action. It is also possible in this way to compensate for wear on the cutter blades to maintain the desired gap without replacing the cutter apparatus.